Commodity products for applications requiring a relatively large volume of the product frequently are shipped in bulk to the point of use. Where the product is a dry fluent material such as a granular or powdery product, bulk shipments may be in hopper cars, where the material is withdrawn from an outlet at the bottom of the hopper. The construction and utilization of such hopper cars is well known to those skilled in the art.
Where relatively coarse or granular materials are delivered by hopper car, those materials can be dumped from the hopper by opening one or more gate valves fitted at the bottom of each hopper. That technique of unloading a hopper car is not feasible with relatively fine or powdery materials such as carbon black. The relatively fine particle size of such materials causes particles to become airborne if the material simply is dumped through a gate valve or another kind of open flow channel. As a result, hopper cars used for transporting carbon black or other relatively fine or powdery materials usually are fitted with a pipe connection at the bottom of the hopper, either in place of the gate valve or as an add-on thereto, for connecting a hose or pipe that transfers the commodity. Reduced air pressure is applied to that hose or pipe, thereby creating an air flow to withdraw the relatively fine or powdery commodity from the bottom of the hopper car.
Once a hose or pipe is connected to the hopper car as described above to withdraw the contents of the hopper, a relatively closed system exists which prevents spilling or airborne dispersion of relatively fine particles during unloading. However, the opportunity remains for unwanted spilling or dumping of the fine material while connecting the delivery hose to the hopper car. Where a hopper car is equipped with a pipe and associated fittings for directly connecting the delivery hose, a cap or other closure must be removed from the pipe before the hose can be connected to that pipe. Given the pressure head that may be present when uncapping a delivery pipe at the bottom of a fully-loaded hopper car, a considerable amount of powdery commodity can pour from the uncovered pipe during the brief time needed to attach a receiving hose. This wasted commodity tends to accumulate at a particular location as a succession of hopper cars are unloaded at that location, creating a messy and potentially hazardous work environment. Spillage during the unloading of a powdery commodity is exacerbated where workers must attach a receiving-hose adapter to the conventional gate valve fitting at the bottom of the hopper car, which can be accomplished only while lying on one's back beneath the car.